Where Have All the Spacemen Gone?Speculations on the Fermi Paradox, Part 1

by Christopher Jones

Original Publication Date: May 31, 2002

As I return home from work each day, the darkness of night already enveloping the world, my two-year-old son and I always linger outside for a few minutes and gaze up at the stars. He likes to call them "little bitty peanuts" -- something his mother said as a joke and which stuck -- and he is totally fascinated by them. So am I; and always have been since I was his age. As we stare up into the blackness, the little twinkles dancing around the sky, we both ask questions. For him, it is “What are they?” For me it is “Where are they?”

In my case, "they" refers to the aliens that surely must be out there. I don't mean those annoying little flying saucers that like to buzz farmers, but rather the other intelligent life that must surely exist somewhere in the visible universe. With billions of galaxies out there -- each filled with billions of stars -- it would be absurd to think that only our little blue-green oasis has seen the spark of life.

Nevertheless, when we turn our ears to the heavens we are met with silence. The Great Silence it is called, in fact -- another name for the famous Fermi Paradox. The Paradox is based on a question once posed by the physicist Enrico Fermi in which he asked why we don't detect any signs of life in the cosmos when the odds are so strongly in favor of its existence. It is a problem that has puzzled our species for centuries, and an idea that goes back to the very beginnings of human thought.

I often stand puzzled at the unswerving faith that the very religious have in something that they cannot see, cannot prove. At the same time, I am no different than them. The only thing that differentiates us is what we believe in. While the lack of any evidence of truth in religion serves as a roadblock for me, the absence of any evidence of extraterrestrial life does not. I am absolutely certain that it exists. It may not be abundant, but somewhere out there it exists. The idea that it could not is simply too absurd. I'm sure the very religious feel the same about their beliefs. Same shoe, different foot.

What is special about our planet and our star system? Nothing. For life to exist here is only proof that it must exist elsewhere. So why do we not detect it despite our ongoing SETI efforts? The problem is rather complex.

Pop culture like Star Trek tells us that all intelligent life in the universe is pretty much on the same playing field. Sure the Klingons have cloaks while the Federation does not. The Federation has transporters while the Kazon do not. What they all have are ships that travel at more of less the same speed, phasers with more or less the same power, and a good command of the English language. "Just minor differences" is what we are told separates the wide assortment of cultures roaming the stars.

In reality, there's a very good chance that at any one time there are but a few living civilizations, each at a very different level of development. But before we get into that, let's take a look at three of the most common solutions to the Fermi Paradox.

1) There is no one out there.

2) There is someone out there, but they have no interest in space travel and contacting others, or they conceal themselves for ethical reasons.

3) When a civilization reaches a certain level of technological development it destroys itself in a terrible war.

We'll talk about these solutions one at a time over the next few weeks. In this first article we are focusing on solution one, which we've already gotten out of the gate.

As I have already said, the general idea that there is no one out there is simply absurd. It is possible, however, to view the question in a more detailed way. The less simplistic approach -- and the one that is most accurate -- is to ask, Is there anyone out there right now?

"Now" is the real key, in my opinion, because in a universe that is 14 billion years old, the odds that civilizations are going to pop up at the same time are pretty low. Random chance says that it will sometimes happen (and I'm speaking in terms of two locales somewhere in the universe as a whole), but I doubt that it is does so very often and certainly not within the same area of space. (Some estimates indicate that there should be approximately 1,000 technological civilizations in the Milky Way at any one time, but this seems rather optimistic.) Unless another civilization within communications range of us popped up at virtually the same time we did, there's a good chance that we won't be able to detect each other.

The reason is that technology changes rapidly. We only gained the ability to use radio waves in the past 100 years, and we're already moving away from them in favor of new technologies. That leaves a pretty small window for two civilizations to cross paths. Stretch that window to, say, 500 years and you greatly decrease the odds. Yet 500 years is but a wink of an eye to the universe. It's like two cars being in exactly the same place when the light changes and colliding in the intersection. For any one driver it is an extremely rare event to become involved in such an incident. Our civilization is a lot like that driver.

To make matters worse, our successful detection of radio waves from a distant civilization would require their use of a focused transmission of enormous power. They would either have to know we were here and point their transmitter right at us or target our star system "blindly" in the hopes that someone would be here. (As an example, in Carl Sagan's Contact the transmission was intentionally aimed directly at Earth because the aliens had detected our presence.) Success also depends on their selection of the "proper" frequency, and even on their use of radio waves for communication in the first place.

Assuming that they do use radio waves and select the frequency that we believe is the proper one, it seems to me that there are two key factors that prevent us from finding signs of other life in the universe. Factor one is temporal. Factor two is spatial.

The temporal part is what I've just been talking about. They were here yesterday, we are here today, and someone else will be here tomorrow. Civilizations rise and fall, missing each other like the husband and wife trying to hook back up on the aisles of a supermarket. If you dropped three people at random locations in an otherwise deserted Texas, do you think they would be able to find each other? Just for fun, make one of them a caveman, one of them a medieval serf, and the other a contestant from Survivor.

The Texas analogy ties in to the second factor: space. Even the nearest of stars are very far apart. Even if the universe is generously sprinkled with advanced civilizations, it is probably rare that any two are very close to one another. If you drop your contact lens in the bathroom sink, it's easy to find. If you drop it on a football field, it is not. Now think about the size of the universe. It's not surprising we haven't found anyone yet.

All of this rambling about Texas, car accidents, and contact lenses is to point out the absurdity of the idea that lack of evidence means lack of existence in the world of SETI. We may look for a million years and never detect a single sign that ET exists. But even then it will not be proof that he doesn't. It will only be proof that we haven't yet looked in the right place at the right time.

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In the next installment of "Where Have All the Spacemen Gone?" we'll look at the far more interesting second solution, the idea that the aliens either don't want to talk or are in hiding.